The Sig instructions say to clean the sight with a lense cloth they provide with the sight or a lense pen, Trijicon sells a pen that uses graphite, doesn't sound great to me. I did a search that showed some using white distilled vinegar and some using alcohol or eyeglass cleaner. I guess eyeglass cleaner or camera lense cleaner would be safe. Just wondering what is a safe but effective way to get nasty stuff like oil, grease or carbon off the lense.